Experts at Chicago's TrustWave said sometimes the emails will have poor grammar or cheap-looking graphics, but others can look legitimate. They said you should never click on or copy any of the links these alarming emails.

"If you get an email from some company and there's a link, don't click the link to log in, just open up a separate browser. Don't do it within your email, go to the browser and go to that site directly," said Shawn Kanady of TrustWave.